1. Field of the Invention
This invention relates to a novel photosensitive composition for dry development in the ultra-fine pattern formation in the semiconductor industry. More particularly, this invention relates to a novel photosensitive composition prepared by adding a bisazide compound to a polymer for giving photo-sensitive properties thereto, said photosensitive composition being suitable for plasma development.
2. Description of the Prior Art
A process for the preparation of semiconductor elements includes photolithography, which comprises: (a) coating a photoresist as a thin film having a thickness of about 1 micron (which will be a resistive film during etching) on a silicon wafer having a silicon oxide, silicon nitride or polysilicon layer having a thickness of thousands of angstroms, (b) irradiating said film with ultraviolet light through a predetermined photo-mask, (c) developing, (d) rinsing, (e) effecting etching of the silicon oxide layer or the like, (f) removing the photoresist, (g) rinsing the wafer well, and (h) allowing an impurity to diffuse through the exposed area of silicon to be implanted thereinto. The semiconductor elements are manufactured by repeating the above photolithography several times followed by the preparation of electrodes and wirings.
Examples of photoresists currently used in the ultra-fine pattern formation of the semiconductor industry include cyclized rubber type negative photoresists such as OMR marketed by Tokyo Ohka Kogyo Co., KMR marketed by Eastman Kodak Co., and Waycoat, marketed by Hunt Chemical Corp.; novolak-type positive photoresists such as OFPR marketed by Tokyo Ohka Kogyo Co., AZ marketed by Shipley Co., KMPR marketed by Eastman Kodak Co., and HPR marketed by Hunt Chemical Corp.
In the process for the preparation of semiconductor elements, the photoresists known in the art are all subjected to wet development and rinse processing to be used as a mask for etching the silicon oxide layer or the like with hydrofluoric acid etching solution and are stripped by use of a stripper, or with an oxygen plasma in a special case. However, selective stripping of the photoresist to exposed areas or unexposed areas by use of an oxygen plasma in the case where the photoresist is exposed to light through a photo-mask (that is, dry development) has never become available prior to the instant invention.
In the conventional plasma processing, oxygen gas is introduced into an evacuated bell jar at a pressure of from 10 to 0.1 Torr. This is followed by the application of a high radio frequency (RF) and high voltage thereto to form a plasma such as an ion, atom or radical of the introduced oxygen gas. The polymer used as the photoresist is decomposed when exposed to the resulting plasma.
The use of an organic solvent in the conventional wet development and rinse processing causes problems, such as a hazardous working atmosphere and a long processing time. Photoresists, especially the negative photoresists, swell so markedly in the developing solution that resolution is impaired.